JavaScript/Glossary

We try to keep consistency within the Wikibook when using technical terms. Therefore here is a short glossary. object An object is an associative array with key-value pairs. The pairs are called properties. All data types are derived from object - with the exception of primitive data types. property A key-value pair that is part of an object. The key part is a string or a symbol, the value part is a value of any type. dot notation The syntax to identify a property of an object using a dot: myObject.propertyKey bracket notation The syntax to identify a property of an object using brackets: myObject["propertyKey"] curly braces notation The syntax to express an object 'literaly' using { }: const myObject = {age: 39} function A function is a block of code introduced by the keyword function, an optional name, open parenthesis, optional parameters, and closing parenthesis. function greeting(person) { return "Hello " + person; }; The above function is a named function. If you omit the function name, we call it a anonymous function. In this case, there is an alternative syntax by using the arrow syntax =>. function (person) { // no function name return "Hello " + person; }; // 'arrow' syntax. Here is only the definition of the function. // It is not called, hence not running. (person) => { return "Hello " + person; }; // or: (person) => {return "Hello " + person}; // assign the definition to a variable to be able to call it. let x = (person) => {return "Hello " + person}; // ... and execute the anonymous function by calling the variable // that points to it: x(...) alert( x("Mike") ); // interesting: alert(x); // execute an anonymous function directly ((person) => { alert("Hello " + person); })("Mike"); method A method is a function stored as a key-value pair of an object. The key represents the method name, and the value the method body. A method can be defined and accessed with the following syntax: let person = { firstName: "Tarek", city : "Kairo", show : function() { return this.firstName + " lives in " + this.city; }, }; alert(person.show()); callback function A function that is passed as an argument to another function. console Every browser contains a window where internal information is shown. It's called the console and normally not opened. In most browsers, you can open the console via the function key F12. item A single value in an array. Same as 'element'. element A single value in an array. Same as 'item'. parameter When defining a function, variables can be declared in its signature, e.g.,: function f(param1, param2). Those variables are called parameters. argument When calling a function, variables can be stated to be processed in the function, e.g.,: f(arg1, arg2). Those variables are called arguments. The arguments replace the parameters which were used during the function definition.